Networks have been changed in that subscribers use broadband networks and services are diversified. Networks that transfer signals from various access networks accommodating subscriber lines have changed from SONET/SDH networks to Internet protocol (IP) networks. MSPP apparatuses corresponding to such diversified services have been developed.
In some cases, an MSPP apparatus is required to process signals transmitted using different protocols. As a solution for such a case, a technique is used in which a SONET/SDH frame is used and asynchronous transfer mode (ATM) signals, plesiochronous digital hierarchy (PDH) signals, and Ethernet signals are multiplexed in the payload section of the frame based on SONET/SDH (for example, refer to Japanese Laid-open Patent Publication No. 2001-186188).
There is a configuration of an MSPP apparatus including interface boards that individually interface with lines corresponding to respective services using, for example, SONET/SDH, Ethernet, and PDH, so as to provide multiservice. With such a configuration, in general, each of the interface boards is provided in advance with circuits (such as photoelectrical conversion circuits and signal termination circuits) that process signals corresponding to the bit rate of the lines accommodated. Therefore, in order to accommodate lines of a bit rate different from the lines having been accommodated after an apparatus is operated, it is necessary to replace the interface board.
Small form factor (SFF) and small form factor pluggable (SFP) which is a related technique to SFF have been developed to facilitate size reduction and standardization of transmission modules such as optical transceivers that transmit and receive signals (optical signals) from the above-mentioned access networks or the like. Communication device manufacturers and communication companies played a central role in establishing SFF in order to carry out size reduction and standardization of transmission modules. SFP has been established to produce pluggable transmission modules that conform to SFF.
Recently, transmission modules conforming to SFP are used in MSPP apparatuses, and thus, it is easy to change the bit rate of a line connected to a port of an interface board. Accordingly, there is an increasing need for an MSPP apparatus capable of mounting a transmission module conforming to SFP and accommodating lines of different bit rates in one port. The transmission modules mentioned hereinafter are transmission modules conforming to SFP.